High-frequency multiplex signaling system



JulyI 29 1924. 1,502,812

L. ESPENSCHIED HGH FREQUENCY MULTIPLEX SIGNALING SYSTEM Original Filed Sebi.. 30. 1919.

535% QM @1Min/w13 L Patented July 29, 1924.

UNITED STATES 1,502,812 PATENT OFFICE.

LLOYD ESPENSCHIED, OF QUEENS, NEW YORK, ASSIGNOR T0 AMERICAN TELEPHONE ,AND TELEGRAIH COMPANY, A CORPORATION OF NEW YORK.

HIGH-FREQUENCY MULTIPLEX SIGNALING SYSTEM.

Original application led September 30, 1919, Serial No. 327,500. Divided and this application led April 16, 1921. Serial No. 461,984.

To all whom it may concern:

Be it known that LLLOYD ESPENSCHIED, residing at Queens, in the county of Queens and State of New York, have invented certain Improvements in Higl1-Frequency Multiplex Signaling Systems, of which the following is a specification.

This invention relates to high frequency multiplex signaling systems and particulari3 to a terminal circuit arrangement em hgdying the use of a common translating Circuit adapted both to modulate the transmitted current and to demodulate the high `Frequency received current.

This application is a division of my co-' pcndin application Serial No. 327,500, filed rreptem r 30, 1919, entitled High frequency multiplex signaling systems.

In the multiplex signaling systems heretofore used which employ a plurality of carrier currents of various frequencies it .has been customary to insert in the transmitting and the receiving branches of the terminal circuit a translating device individual to each of said branches. It is the .object of the present invention to adapt the terminal circuit arrangement so that the processes of modulation and demodulation and amplification of the various currents u both the transmitting and receiving branches of the terminal circuit may be performed by a single translating device. Although the preferable form of translating device isa single thcrmionic vacuum tubc or a plurality of such tubes in combination adapted to function as a single unit with respect to the two branches of the terminal circuit, yet any Well known type of transla/ting device such as the mechanical repeater may be used.

Another 'object of this invention is to provide a terminal circuit arrangement ,which does not require line balancing networks and inwhich the transmitted and rcceived currents are guided through the terminal circuit by means of suitable selecting networks.

Other and further objects of this invention will become apparent from the following description when read in connection lwith the attached drawing of which Figure 1 shows a circuit arrangement having a halanoed duplex modulating and demodulating device which prevents the transmission therethrough of the unmodulated carrier frequency; Figure 2 Shows a terminal circuit having atranslating circuit comprising both an amplifier and a modulating and demodulating device, the said amplifier being arran ed in a feed-backI circuit designed to osci late at the carrier frequency; and Figure 3 has a translating circuit similar in general to Figure 2 but designed to sup press the low frequency component impressed upon the modulating and Ademodulating device.

Figure 1 shows a terminal circuit arrangement in which no artificial lines are employed to balance the low frequency or high frequency transmission lines. ln the circuit arrangement shown in this figure, the low frequency voice currents of line Ll are impressed upon the terminal circuit by means of the transformer TV These low frequency oscillations in circuit 2 ass through the l-ow frequency filter TF1 and are impressed upon the translating circuit by means of the transformer T4. The translating circuit is preferably that shown in the patents to J. R. Carson 1343306 and 13433074each dated June 1.5, 1920. The low frequency oscillations which are impressed upon the circuit modulate the high fri quency carrier current and the modulated wave is impressed upon the circuit 5 by means of the transformer T6. These high frequency modulated waves pass through the high frequency filter TF: and are imresscd upon the. main transmission line All'u hy means of the transformer T4.. In a similar manner the oscillations which are received over the main transmission lincML pass through circuit 8 and the high frequency receiving filter RF, and are impressed upon the translating circuit hy means. of the Itransformer T,l These high frequency modulated waves are demodulatcd in the said circuit b v means of the high frequency carrier oscillations. and the low frequency modulating current is impressed upon circuit 5 by means of the transformer Tw These low frequency oscillations pass .through the low frequency filter RF2 and are impressed upon the low fre cuit Ll by means of the trans It will be apparent that the low voire currents transmitted over uency cirormer T1.

frequency. ,i r circuit-lili" may also be impressed upon circuit 3 by means of the transformer T1, and will pass through the filter BF2 into the circuit 5. Since, however,l the filter TF2 is desi ed to pass only high frequency oscillations, none of the low frequency oscillations will pass to the main line ML and furthermore, since the low fre uency oscillations will be impiessed upon t e plate side of the translating device, substantially no effect. will be produced in the translating circuit. In a similar manner the'received high frequency oscillations may pass into both circuits 8 and 9. Those which pass into circuit 9 may be transmitted through the filter Tl"2 into the circuit 5, but cannot pass into the low frequency circuit L1 on account of the presence of the low frequency filter RFQ, and likewise produce no substantial effect upon the translating circuit, since they are im ressed upon the plate end of the trans ating circuit. If 4 same sido bands are transmitted in both directions through the terminal circuit shown in Figure 1 the amplification produced by the modulating and demodulating device must be limited nto the loss in the terminal circuit itself, that is to say the loss through the transmitting and receiving ath rom the transformer '11 to the transe ormer T1 or vice versa. Further amplification than this would tend to produce singing around the circuit, since the high frequency and low frequency circuits are not balanced by artificial lines. If, however, we-transmit -the upper side band and receive by means of the lower side band then we may obtain greater amlplification without singing, because the ilter TF.z would be designed to transmit only those frequencies comprised within the upper side band of the carrier fre uency and the filter RF1 would be designe to ass only those frequencies lyin within the ower side band of the carrier frequency, consequently the oscillations traveling outward from the circuit 9 Would notbctransmittcd back through the circuit 8 to the modulating and demodulating device on account of the fact that the filter RF1 would not pass the transmittal band of frequencies.

The circuit La represents a low frequency signaling circuit having therein a low frcquency filter l?El by means of which currents of the voice frequency for ersmple may be impressed upon and transmitted over the main transmission line ML simultaneously with the transmission of the hands of high frequency modulated carrier oscillations.

Figure 2 show's another form of terminal circuit, which is characterized by the absence of balancing networks and is also characterized by the use of the opposite side bands of a common carrier frequency for what may be termed the east and west, channels of transmission. Since the frequencies the Y transmitted and received are different, the filters in the two sides of the circuit are adapted to prevent the passage of a common frequency, consequently the circuit will not sing over either the low or high frequency side, and networks for balancing the low frequencyand the high frequency lines may be avoided. In the figure L1 represents a low frequency line connected with the fourwire circuit having a low frequency baud filter Fl and a high frequency band filter F2 in the transmitting path of the terminal circuit, and a high frequency band filter Fa and a low frequency band filter F4 in the receivin path of the terminal circuit. The input si e of the transmit-ting and receiving aths is connected with the oscillator UA1 y means ofythe transformer Tx. The out put side of the oscillator is connected 4withv a modulatin and demodula'ting device MDX by means o the transformer T2. The out. put side of the device MD1 is connected with the output side of the receiving and transmitting circuits by means of the transformer T3. Included in Ithe transmitting path is a filter Fw Whose function is to exclude from the transmitting path of the terminal circuit a group of frequencies ranging from the carrier fre uency to a frequency in the neighborho but somewhat below the lowest frequency transmittcd by the band filter F2. The terminal circuit B shown shown at the onposite end of the main transmission line ML is similar to that described, excepting tha-t the amplifying device A2 shown in the said circuit is non-oscillating.

This circuit arrangement will be better understood from the following description of its method of operation. Low frequency si gnaling currents arriving over the line L, pass through the filter F, and are impressed upon the oscillating-amplifvingdevice OA.. These oscillations are amplified and together with oscillations of carrier frequency generated in the device OA1 are impressed by the transformer T2 u on the modulatin and dcmodulating device MDV The. two ands of frequencies based upon a common carrier frequency are transmitted' together with the carrier requency tothe branch 2 of the transmitting path. The filter F2 is designed to transmit only that band which is desired for transmission in that direction, the other baud being suppressed. The carrier cur-- rent is suppressed by the filter Fw so that the only frequencies fiowing to the mam transmission line ML from the modulatordcmodulator MD, are those contained in thev lll) band which is allowed to pass through the filler F2. The oscillations of carrier fre quency which are generated by the device A, will be impressed by the transformer Tx upon the circuit 3, and pass through the band filter Fa to the main line ML so that the Lucaniavice'both thefcarrier oscil ations';andthef'side`f band oscillatlons are amplifiedfalndare:

.by means o f. the.. transformer 1 '11,4 la

.through thelow frequencyband lter F. to; the floyv'frequency line L.- mg circuit s own in Figure 3 differs-from the foregoingn that' it-is designed to bal- :am

' quenband filter r oscillations arefthereby am lifiedlan'dltoi.

atnvlevice -MDvrby means ofvtransformer frequency currents resulting therefrom ,are

upon Vthe circuit 4.',Q'1'hes'currents`pass Loiv frequency currents set up inthe line L, by means of the signaling'a'paratusnssociated therewith ass throught e low freto the amplifying.de vice 1 These currents together :with thefj non-modulated carrier oscillations nrivinf;r

from the" terminal circuitfatlthefother;'endof'the same lineare impressedsimfult'tt n'eousfV upon theY modulatixrfl e u vice MlDandare-In 'modulated high ,.jfreq'u'en rier; frequency.-'i Filterf F; .is inserted the transmitting circuitf..to'f'su' pressthe' frequency. The frequencxesftransmittedby filter ]5a pass over the transmissionlne ML," through the'flter F.and are impressed up-V on the amplifying device'OA,. The received gather with the cari-ier osci latons arising* within the deviceOAiy itself are'impressed upon the modulatin and demodulating de vice MD,. The recelved hand of modulated frequenciesv are de modulatcd, and the resulting low frequency currents 'pass through the filter F, and the line Ll to `the snalin'g ap-4 paratus associated therewi th. c type 'of modulating and d'emodulatinv device represented by MD, and MD, is ad'pd 'to ehminate the amplification'components of both t-hc'high .frequency and the low frequency oscillations-Iso as'to' prevent singing around the tivo sides ofthe terminal' circuit. One

1of the .advantagesof the 'circuit arran ement shown in this figurearises from t e' use of opposite side bands ofthe carrier frequency whereby balancing networks. are

and demo e oseillationsof'the side'bandiare' de z mdulatedin the devices MID;v and the low ended tage arises from 'the transmittal of ixiglfffrcquencycarrier oscillations from one termnal circuit to another'ter'minal circuit'whereby` identit ,of frequency cf tl\e modulating ulating. current is assured. 3 shows a circuit arrangmmmt die'rin .slightlyfrom that shown. n- Fig- .um he-principaldi'rence arises in the structure of the translating' circuit associatanoed- A I nodulating and demodulatng cir- :cuit .was of a type 4designed to' balance out and-'therefore e inatethe' ,amplification compnentscf both the .high frequencynnd the low fr uency currents. The oscillatance out only the amplification components of the, 'lon frequencycu'rrcnts. `The earr the ,lzirtsformerf` 'Il are together impressed bygtlie transformer T2; upon .the modulating ri -Jaritl'fdemodulatin'g device .MD,. ,It will be Mythewindings of the transformer da thatihemiddlecoil;C, is 'cil C,"x`vhich is connected in `the 'ducbfoxofthe duplexl translating Thefcoil C, fis: l.'raversecl-b3"4 the currents in consequence of reqlic'noy currentsw ill lie im- "cqinmon conductor, The transmitv rimarly thehigh a xllatins so t tthe saidoscillagngsedjacross the input side of n "cjcuit jThe transformer T3 .co'nn 'ted'xvit thejoutput side of the device 'iplurlityoffcoils connected with connected in-''the xnanner 'shown' in the drawing.' The high frequency oscillations impressed bv the collsCJ' and C4 upon the inputsideof the.'translatintr device cause 11u 'corresponding iiuctuations in the output side. of4 the said device, which in turn V'former T' so.that t e low fequencycom- Ponent is balanced out and eliminated. 1t

wllfthus be seen thaty the arrangement' 'shoivn in Figui-e3 provides a suitable means forbalancin out the low frequency; component andt `e` arran ement shown 1n. Figf ure 2 to-balnce out t e,amplilicator'ccm;A ponntsof both frequencies Awhen 4such is desire Itvgis'ill be seen thatthe invention disclosesI 130 in' this application comprises 'a terminalcharacterized bya translating-circutc`cinfcircuit arrangement chariicterized by the abin on to the' tra', and rcceiviiiggpgths sence nf'balancing networks 'to balance ther of-the fourwire circuit and h aving'sgsogrce.' connectin 1ine-circuits;' and further elixir#r oz' -carrier frequency 5 acterized; 'y a'jtransiating circuit common' therewith, the of; si Vingigillvliiclil) to'the 'transmitting und receiving paths-of consists generatingchrrier" uencyA-iuii- ,-"thc'terininal circuit adaptedto modulate-rentiamplifying*thejcurrentsjof cqliiindof und -demodulate the currents impressed frequenciesjtransmittedbypne-o en' "tliereon.' The invention also comprises circuits, deiiiodulating the.,

lci'neans for'generating carrier frequency -os- "said band by'tliecarrier current 1.' cill'ationsand transmitting them tothe terting the` current produced by suclir'fde u' '.xiinzil 'circuit attlieotherend of they con` -lati'on and suppressing the transiui'sso fof;

necting"linecircuitand 'reamplifying the the' carrier frequency current? f carrier-frequency oscillationsbe ore irnp'resS- 4. "Ii1 iihigh :frequencyl ,signaling i i3 ingtliein-'upon' thecommon modulating and comprisingtwo line, circuitseach transmit -80 -.`demodi ilating dc'vice. i j ting a f,t eqi.ieii iy different froiiithatjofthe Although the invention'. has been fills-'. other and nnectedbyfs four-wirer'cfircuit closed in certain particular forni's' and archaracterizedhy l's'ftransliiting', circuit;coi i;'i-.. rangements of parts'it is to be'understood ;moii to theirs @ping-ga paths 21'! 'ttliat th'efinyention is=not thus limited but of'thefour-yvire circuit andI isfyjin'ggiis :-'iir c e'V 85, is capble-'of embodiment in other. und dif, of cuijrierf4 "iiency current sspcifiedthr 'i ferent' fornis n"ithoutdeparting 'from the with,the nilcodofsignalng yspirit and scope of 'tlieappended claims 1in"simultneoiislyimgdmangz. ghggai-gigrg -What lis `claimed` i$ Q f- -frcquencylin iicqord'ncci'withtheLfrejiiicy 2" 1.' In. a signaling syst the-combination transmitted" ylonliiiejgciri'uit, undfdemqdu. 90 with a. high frequency transmission circuitleting tli u euc Qtrsi'ismittgd "byrthe' of' low' frequency signaling ,ircuits, f our- .other lin circiiitlaii transiti "u'ire connecting circuits individuel to the1.jquencies= .resulting said sivnalng circuits adapted to co'nnectf anddeinodulatioxn fhthe said transmission-circiitgwith"eachig- 5. I n afsigrfelip'g J.tlil u "nailing circuit,'eiicli fourfrccircuit hyflgf. with at lowgfteiien ysig aling'-ci' @translating4 circuit connected therewith, high..frequencyf-fsignilinginit-cuit,r

lto nerat'e'oscillatins' of cui-tier frequency connected thereiritli5i-andi'neiifsut 35 an the'otherv translatin' circuitI connected low-frcquencyniidhighfrequenti iireiits. 00

withthecorres nding'j ourfivire circuit nt upon the.translating-circiiitflfroiii theopposteeeii. of the said-transmission cirspectivel s ignalingcircuitsthe ILS- vcuit hiiiiiiig- .means to amplify oscillations of lating circuit' hiiviii'g means to generate l'iigh" 4 the carrier frequency transmitted over tiiclfrequency carrier --currents toliin'lify the 440 saidftiiii'nsinission circuit from the said {ii-st impressed currents fand" to inodu ate- Land 105 transiiiti'i'i'g circuit. dcinodulate the amplified currentsbji'ne'ans 2. In a signaling system the combination of the generated carrier currents.` with tlie high frequency transmission cr- 6;.In a si 'aling system,'tlie comli'in. ion. -cuit'of it low frequency signalin circuit, s. with e low requncy signaling circuit fa impress lou' frequency and high frequency wire connecting circuit ia-racterized by-ia i currents upon the translating circuit from translating circuit bridged across the tufotheii respective signaling circuits, the said Wire branches ofthe four-wire circuit, and connecting circuit 4having ,nssociatcd theie- -rneans to inipressloiv. frequencyandhigh :TV with n translating circuit com rising aii frequency currents u pon the titanslsting-cir'- 1 l5 amplifying circuit having n fee -back concuit from their respective signaling circuits,- nection tuned to n definite frequency dethe said triinsliitingv circuit comprising a signed to. eneriite carrier frequency scilfeed-backoscilliitioncircuit designedto gen#- latiOnS, an also to amplify currents of other erste cari-ien fre iiency current, and. modus "ff frequencies impressed thereon', and a inodu.- latingf and Yclem ula/ting circuit adapted-to 120 latingdemodu ating circuit-,ada tedto iehave impressed hei-con a carriercurrent .ceive th'e carrier current and'sai othe'rcurand alsccurrents impressed upontlie fourrents;andtcliaracterizcd byineiins to modu- Wirecircuit 'by` the: low frequency' and the late and demodulntesaidothcr currents, and high fre uency signalinggcirciits whereby G0 also by means to suppress the linear com' the said atter currents liniiybe modulated 125 ponentsof modulation and demodulatioii. and tlemodulzited.` 'g' i 3. Iiil a -liigh frequency signaling system' -7. In ii signaling 'systcmythe combination comprising two line circuits each transmitwith u high frequency transmission -circuit ting a frequency different fromthat'. of the-fof;- loiv frequency signalingcircuits, four- 5 'otherfimd connectedbf.' a four-'wire circuit f'ivirc connecting circuits indiy'igliialjd each, 13-

signaling circuit and connected with the said transmission circuit,l each of said four- Wire circuits having a translating circuit connected therewith, and means to impress low frequency and high Afrequency currents upon the said translating circuits from their respective signaling circuits and from the transmission circuit` each translating circuit embodying a feed-back oscillation circuit and a modulatingdemodulating circuit, the said modulating-demodulating circuit having;r its input and output sides conjugately related to suppress both the carrier and the signaling currents, and to transmit only the currents resulting from modulation and demodulation.

8. In a signaling system, the combination with a high frequency transmission circuit. of a low frequency signaling circuit, a tourwire circuit connecting the said transmission circuit and the said signaling circuit and having a translating circuit associated therewith, and means to impress low frequency and high frequency currents upon the said translating circuit.y the said translating circuit having means to generate high frequency carrier oscillations and also to amplify low frequency signaling currents and high frequency signaling currents impressed thereon, a second low frequency signaling circuit and second four-w1re connecting,r circuit having a translating cirA cuit containing means to rcamplify oscillag tions ot carrier frequency received over the said transmission line from the said first mentioned four-Wire circuit and to amplify other currents impressed upon the said second translating circuit.

9. ln a signaling system, the combination with a high frequency transmission circuit of a low 'frequency signalingr circuit, a tour- Wire connecting circuit having associated therewith a translating1 circuit comprising an amplifyingr circuit having a feedback connection tuned to a definitefrequency, and means to impress low frequency and high frequency currents upon the said translatinrr circuit from the said signaling circuits` the said translating circuit having means 1o generate carrier frequency oscillations and to amplify currents of other frequencies impressed thereon, und a modulatiligalemoflulatingcircuit haring means to receive the carrier current and the said other currents anal to modulate and lemcijlulate the said other currents.

ln testimony whereof` l have signed my name to this specification this 15th day of lpI'll. 1921.

LLOYD ESPENSCHIED, 

